PHP IoC cross dependencies

Question

So we've got a container, service providers and, with inversion of control, we can do fancy stuff like:

public function __construct(CarServiceInterface $carService)
{
}

And things get resolved nicely because somewhere else...

$container->bind(CarServiceInterface::class, function ()
{
    return new CarService();
});

Let's say car service depends on human service. Then...

    $container->bind(CarServiceInterface::class, function (Container $container)
    {
        return new CarService($container->make(HumanServiceInterface::class);
    });

Hey, that works. Cool.

But then suddenly humans NEED cars, and the human service is built like this:

$container->bind(HumanServiceInterface::class, function (Container $container)
{
   return new HumanService($container->make(CarServiceInterface::class);
});

Voila, cross dependency.

How to solve this?

Is this consequence of a flaw in the design?

Thanks!

Co-dependence is not healthy – Orangepill Sep 03 '15 at 14:02 — Orangepill, Sep 03 '15 at 14:02

score 2 · Answer 1 · edited May 23 '17 at 12:06

2

I think this would be called 'Circular dependencies' (see here for more about this).

The answer says that there's no way to do this, and that the only way to use a circular dependency is to use setter injection, instead of the usual constructor injection.

edited May 23 '17 at 12:06

Community

1
1

answered Sep 03 '15 at 14:01

jeroenvisser101

856
10
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This is a good answer. Human's don't _need_ cars, but if one's available they certainly could use one. – Jeff Lambert Sep 03 '15 at 14:19
@watcher Thanks, and I agree, if you compare it to a real-life scenario, it makes a lot of sense as well. – jeroenvisser101 Sep 03 '15 at 15:10

PHP IoC cross dependencies

1 Answers1